Piano World Home Page Forums Our Most Popular Forums Digital Pianos - Electronic Pianos - Synths & Keyboards Modified Headphone Plug for P85/95

I'm thinking it might be possible to machine down the contacts of a stereo phone plug so they still connect but don't open the contacts that disconnect the speakers. This would allow a "line out" of sorts. I like the sound and feel of the vibrations through the keys, but want more volume with an external amp/speakers. Thought about shorting the speaker-disconnect contacts internally but that involves taking the keyboard apart which I'm not brave enough to attempt.

Interesting idea. I agree, I hate that the speakers stop giving your fingers that nice authentic-feeling vibration as soon as you want to plug into an amp. Some of the Casios have the same problem.

Like you, I have entertained the thought of opening them up and doing some surgery, but am not sure how easy it would be. One model I looked at once had the whole headphone jack encased in a little sub-assembly, with no easy obvious way to get to its individual connections.

Getting the dimensions of the contacts just right will be a challenge. I'll likely have to sacrifice a few plugs to determine the min and max thickness, then aim for the middle. Wish I had a 1/2" power drill to use as a lathe!

This may help......or not :-)
http://upload.wikimedia.org/wikipedia/commons/a/af/Jack-plug--socket-switch.jpg
The contacts at the top of the pic, would normally be closed, providing a circuit to the speakers, so you would need to machine the tip down, but still provide enough metal to make contact, but avoid breaking the circuit.

Be much easier to make the mod inside the piano.

On my Kawai CP136 type "C" is used:


I think it is necessary to use this type, because an isolated contact is needed.

In this case it is impossible to modify the plug. So if you dont know what is used inside, you have to open it anyway....
And if you have it open, it is easier to modify the piano.

Was easy for me. It is an external box that is hold only by 3 screws ;-)

I have to agree with hpeterh.

You can't expect to defeat the speaker/headphone-switching of the socket by modifying the plug.

Better to open up and wire in separate jacks to provide the needed outputs.

You don't have to modify the jack. For $2 you can buy new jacks.

But you shouod not have to modify or replace a jack, why not simply wire a jumper across the switch so it will always, in effect remain closed. All you ned is one ich of wire and solm solder.

The only problem I see is that now your headphones and speakers are wired in parallel and you will have no way to adjust to relative volume, The ratio of headphone to speaker volume would be fixed. So you likely need to run the headphone through a small headphone amp simply so you can have adjustable gain on them. The headphone amp would likely have high input impedance and, that is something you want if for a device that is wired in parallel with the speaker

For my piano it is different: Headphones and speakers are not parallel. (I cannot adjust the volume independently, but a passive loudness regulator should do this if required)

That is, because the piano has a dedicated headphone amplifier.
So the plug does not switch any audio signals, it switches a control voltage that switches the speaker amplifier off.

If a piano has two headphone outputs, then it probably always made this way, the amp is switched off or the audio signal is switched with a relay, otherwise it would not be possible that 2 plugs independently disable the speakers.

So - at least in my case- it was easy to modify only one plug. The other plug is unmodiefied and disables the speakers.

I did this, because I record MP3 from the Speaker outlet.

BTW, Headpones + speakers parallel should not be a problem, because the phone has much higher impedance, even if it had only 40 Ohm, this would modify the total impedance by about 10%. Also the Headpone Outputs must have overload protection for this (not so unprobable) case that somebody plugs in a bad phone or a noncompatible (Mono) plug.

Best,

Peter

The chances are is that the sockets have been wired in a certain way. Look up 'normalling' and 'half-normalling' on the internet. Half normalling is commonly used in mixing desk inserts as well as many outboard units like compressors and mic preamps that benefit from insert send and returns.

If normalling is the reason the feed to the amps input is broken when you insert headphones, then you could potentially de-wire the offending connection. If it were me, I'd wire a panel switch so you can choose when the amps inputs are feeding one or both amps regardless of whether the phone jack is inserted or not.

Regards. Rimmer

I agree that jumpering inside the jack is easier but the goal here is to defeat the speaker cut-out without opening the case. If the jack area were separate then obviously it's easier to open just that area, but believe jack access on the P85/95 requires opening the entire case.

I don't think it's impossible to modify a plug to work, but it won't be easy either.

I don't know about the Yamahas, but I can tell you that getting to the guts of some of the Privias can be a bit of an ordeal.

If you do figure out how to make a plug work, you might have a little something you can market on eBay!

Hang on a minute. I just re-read your original post.

Are you saying you want to send a line out of the keyboard to an amplifier, plug in the headphones and still have the internal speakers working?

If it's just a matter of having the speakers working with the headphones plugged in (not line out to external amp) then buy a cheap headphone amp, something like this (although I rarely recommend Behringer so it's for example only, however it might be okay). You can then pop the headphones in to the mixer and your done.

If you want both the internal speakers and amplified line out working, I don't know if the internal speakers defeat when the line out is connected though, I seriously doubt it, probably with the headphones, then the easiest way out is to purchase a little mixing desk and some cables.. Something like this . Again, i'm hitting the cheapest options here as you might not want to shell out on something more expensive. If your not worried about the money, then something a little more up market is highly recommended..

Regards. Rimmer

Rimmer, the issue is that the *only* output of the P85/P95 is the headphone out, it serves dual function as also being the unit's line out to an external amp. The problems is that the internal speakers shut off whenever you plug anything into that jack. That's usually what you want when plugging in headphones, but at least for some of us, not what we want when we connect to an external amp.

The annoying thing is that there are two of these outputs on the Yamaha and they are wired exactly the same. It would have been better to wire one one way and one the other. But the intended purpose of the second jack seems to be that two people can both be wearing headphones, so they both turn off the internal speakers.

Got ya..

I'll rethink...

Well, I tried the filed-down stereo plug thinking I would reach a thickness where the signal contacts were still there but the speaker-disconnect contacts hadn't been pushed opened. No such luck... the plug essentially fell apart because I had removed so much of the contacts, and speakers still got disconnected when plugging it in.

Perhaps a custom-machined plug would work but that's beyond my capabilities.

Even a custom-worked part wouldn't do it.

If the thickness of the plug is adequate to press on the contacts in the jack, then those same contacts will spring back slightly ... and disconnect the internal speakers. That's their job.

If you thin the plug so it just barely touches the jack contacts, then the contacts might not retract, allowing the internal speakers to play. But then you'd have a very unreliable connection at the jack (because of inadequate pressure against the contacts).

It just won't work. Instead, just open up the case and wire in an extra phone jack.

I've done this:



It's not hard, and works great.